info wanted on obscure chemistry: Al-Fe2O3: repost from endless sphere
has ANYONE heard of these things before, I have been told a former UMass Lowell professor worked on them, and I have met people who have heard of them but have never once met someone with useful info on them.
The following is copied from endless sphere. it contains quite a bit of educated guesses and information from third or greater hand sources, and I need help filling in the gaps.
I am trying to find more information on aluminum iron secondary batteries.
What i do know is that they were first built at Texas A&M university in 1994, funded by the army in order to power long range series hybrid military trucks. I am unsure but to the best of my knowledge they had a large amount of magnesium added to the aluminum anode so that instead of forming slightly soluble aluminum hydroxide it would instead form an insoluable complex ion; hydrated magnesium aluminate, normally known as hydrated common aluminum spinel. the prototypes were crude flooded plate pocket cells very like the old Edison Nickle Iron or early flooded NiCd types. They claimed between 380 and 450 wh/kg with these early types, and considering most of a plate pocket cell is not the electrode I believe there is large room for improvement on these figures.
Unfortunately there is no free lunch and there are severe drawbacks to this chemistry. Specifications were not available but I have personally spoken to Dr. Ziyad Salameh of the Massachusetts battery evaluation laboratory at the University of Massachusetts in Lowell on the issue of aluminum iron batteries, and we agree on several likely problems. First the severe shape and volume change of the anode will leave it with a cycle life no better than a big box mart quality lead acid system. Secondly the terrible electrical conductivity of spinel will guarantee high peukert losses, high internal resistance, overheating problems, poor efficiency with regards to charging, and require long charging times. The batteries will also require frequent watering, and the voltage is so high that any overcharge or attempt at fast charging will result in the water being dissociated into hydrogen and oxygen, creating a fire hazard thereby preventing unattended charging, trickle charging, or use of a simple, cheap charger.
I have also read of a 3 volt open circuit, 50 ah at C/10 "D" size battery using this chemistry, in a table comparing and contrasting available batteries to laboratory exotics. the paper was published in 2001, and i can no longer find it. The only google-able copy of it was forcibly removed from scribd for copyright infringment a year or two ago. I believe this was a bobbin electrode type, like used in primary alkaline cells, because to achieve this astonishing volumetric energy density nearly the entire battery would have to be active electrode material. unfortunately when wired in very high voltage strings they would sometimes put on a wonderful impression of a thermate grenade, spewing molten iron farther than a garden hose sprays water. what I am guessing happened, but cannot know for sure without obtaining full specs, is they may have used flimsy separators and used pasted electrodes for both anode and cathode. Failure would likely proceed as follows; 1: separator gets compromised, 2: anode and cathode touch each other through hole in separator, 3: short circuit causes internal plasma event, creating enough heat to melt anode and start a thermite reaction. 4: BOOM.
While inherently a risky combination, I see no reason why strong separators and sintered or polymer bound electrodes would make an acceptable battery. It would require giving up the 50 ah d cell, but even the early plate pocket cells were a large improvement over the latest rc grade LiPO's
Does anyone know if any group is making a safer version of these on a commercial level, and if so where do I buy them. A 400 km range ebike sounds too good to pass up. These cells would also likely be a godsend to anyone looking to make a long range version of the tidalforce or any similar battery in wheel system.